Content for  TS 24.501  Word version:  19.0.0

The purpose of the UE-requested PDU session modification procedure is:

1. to enable the UE to request modification of a PDU session;
2. to indicate a change of 3GPP PS data off UE status for a PDU session;
3. to revoke the previously indicated support for reflective QoS;
4. to request specific QoS handling and segregation of service data flows;
5. to indicate to the network the relevant 5GSM parameters and capabilities (e.g. the UE's 5GSM capabilities, whether the UE supports more than 16 packet filters, the maximum data rate per UE for user-plane integrity protection supported by the UE for uplink, the maximum data rate per UE for user-plane integrity protection supported by the UE for downlink and whether the UE requests the PDU session to be an always-on PDU session in the 5GS) for a PDN connection established when in S1 mode, after an inter-system change from S1 mode to N1 mode, if the UE is a UE operating in single-registration mode in a network supporting N26 interface and the UE has not previously successfully performed the UE-requested PDU session modification to indicate to the network the relevant 5GSM parameters and capabilities;
6. to delete one or more mapped EPS bearer contexts;
7. to convey a port management information container;
8. to re-negotiate header compression configuration associated to a PDU session using control plane CIoT 5GS optimization; or
9. to enable the UE to request to join or leave one or more multicast MBS sessions associated with a PDU session.
10. to send the URSP rule enforcement report to the network associated to:
    1. an established PDU session; or
    2. a PDN connection, after an inter-system change from S1 mode to N1 mode, if the UE is a UE operating in single-registration mode in a network supporting N26 interface.

When the UE-requested PDU session modification procedure is used to indicate a change of 3GPP PS data off UE status for a PDU session (see subclause 6.2.10), the UE shall initiate the UE-requested PDU session modification procedure even if the UE is outside the LADN service area or the timer T3396, T3584, T3585 or the back-off timer is running or is deactivated. If the UE needs to revoke the previously indicated support for reflective QoS for a PDU session and timer T3396, T3584, T3585 or the back-off timer is running or is deactivated, the UE shall not initiate the UE-requested PDU session modification procedure and shall instead initiate the UE-requested PDU session release procedure. If the UE needs to initiate the UE-requested PDU session modification procedure to indicate to the network the relevant 5GSM parameters and capabilities (e.g. the UE's 5GSM capabilities, whether the UE supports more than 16 packet filters, the maximum data rate per UE for user-plane integrity protection supported by the UE for uplink, the maximum data rate per UE for user-plane integrity protection supported by the UE for downlink and whether the UE requests the PDU session to be an always-on PDU session in the 5GS) for a PDN connection established when in S1 mode, after an inter-system change from S1 mode to N1 mode, the UE is a UE operating in single-registration mode in the network supporting N26 interface, the UE has not previously successfully performed the UE-requested PDU session modification to indicate to the network the relevant 5GSM parameters and capabilities, and:

1. timer T3396, T3584, T3585 or the back-off timer is running, the UE shall initiate the UE-requested PDU session modification procedure after expiry of timer T3396, T3584 or T3585 or after expiry of the back-off timer; or
2. the UE is in substate 5GMM-REGISTERED.NON-ALLOWED-SERVICE and has not performed the the UE-requested PDU session modification procedure (see subclause 5.3.5), the UE shall initiate the UE-requested PDU session modification procedure after entering substate 5GMM-REGISTERED.NORMAL-SERVICE.

In order to initiate the UE-requested PDU session modification procedure, the UE shall create a PDU SESSION MODIFICATION REQUEST message. The UE shall allocate a PTI value currently not used and shall set the PTI IE of the PDU SESSION MODIFICATION REQUEST message to the allocated PTI value. The UE shall not perform the UE-requested PDU session modification procedure for an emergency PDU session, except for a procedure initiated according to subclause 6.4.2.1, item e) only, and for the error cases described in subclause 6.4.1.3 and subclause 6.3.2.3. The UE shall not perform the UE-requested PDU session modification procedure for a PDU session for LADN when the UE is located outside the LADN service area except for indicating a change of 3GPP PS data off UE status. If the UE requests a specific QoS handling and the PDU session is not associated with the control plane only indication, the UE shall include the Requested QoS rules IE indicating requested QoS rules or the Requested QoS flow descriptions IE indicating requested QoS flow descriptions or both for the specific QoS handling. The Requested QoS rules IE includes the packet filters which describe the service data flows requested by the UE. The specific QoS parameters requested by the UE are specified in the Requested QoS flow descriptions IE. If the UE requests the network to bind specific service data flows to a dedicated QoS flow, the UE shall create a new QoS rule by setting the rule operation code to "Create new QoS rule" and shall set the segregation bit to "Segregation requested" for the corresponding QoS rule in the Requested QoS rules IE. The UE shall set the QRI values to "no QoS rule identifier assigned" in the Requested QoS rules IE, if the QoS rules are newly created; otherwise, the UE shall set the QRI values to those of the existing QoS rules for which the specific QoS handling applies. The UE shall set the QFI values to "no QoS flow identifier assigned" in the Requested QoS flow descriptions IE, if the QoS flow descriptions are newly created; otherwise, the UE shall set the QFI values to the QFIs of the existing QoS flow descriptions for which the specific QoS handling applies. The UE shall not request to create more than one QoS flow in a UE-requested PDU session modification procedure. If the SMF receives a PDU SESSION MODIFICATION REQUEST message with a Requested QoS rules IE containing more than one QoS rule with the rule operation code set to "Create new QoS rule", the SMF shall assign the same QFI to all the QoS rules which are created. If the UE requests to join or leave one or more multicast MBS sessions associated with a PDU session, the UE shall include the Requested MBS container IE in the PDU SESSION MODIFICATION REQUEST message and shall set the MBS operation to "Join multicast MBS session" for the join case or to "Leave MBS session" for the leave case. The UE shall include the multicast MBS session information(s) and shall set the Type of multicast MBS session ID for each of the multicast MBS session information to either "Temporary Mobile Group Identity (TMGI)" or "Source specific IP multicast address" depending on the type of the multicast MBS session ID available in the UE. Then the remaining values of each of the multicast MBS session informations shall be set as following:

1. if the Type of multicast MBS session ID is set to "Temporary Mobile Group Identity (TMGI)", the UE shall set the multicast MBS session ID to the TMGI; or
2. if the Type of multicast MBS session ID is set to "Source specific IP multicast address for IPv4" or "Source specific IP multicast address for IPv6", the UE shall set the Source IP address information and the Destination IP address information to the corresponding values.

The UE should not request to join a multicast MBS session for local MBS service if neither current TAI nor CGI of the current cell is part of the MBS service area(s) of the multicast MBS session, if the UE has valid information of the MBS service area(s) of the multicast MBS session. For a PDN connection established when in S1 mode, after an inter-system change from S1 mode to N1 mode, if the UE is a UE operating in single-registration mode in a network supporting N26 interface, the PDU session is of "IPv4", "IPv6", "IPv4v6", or "Ethernet" PDU session type, the PDU session is not associated with the control plane only indication:

1. the UE is performing the PDU session modification procedure to indicate the support of reflective QoS and the UE has not previously successfully performed the UE-requested PDU session modification to provide this indication, the UE shall set the RQoS bit to "Reflective QoS supported" in the 5GSM capability IE of the PDU SESSION MODIFICATION REQUEST message; or
2. the UE is performing the PDU session modification procedure to indicate that reflective QoS is not supported and the UE has not previously successfully performed the UE-requested PDU session modification to provide this indication, the UE shall set the RQoS bit to "Reflective QoS not supported" in the 5GSM capability IE of the PDU SESSION MODIFICATION REQUEST message.
   If the UE is performing the PDU session modification procedure to revoke the previously indicated support of reflective QoS and the PDU session is not associated with the control plane only indication, the UE shall set the RQoS bit to "Reflective QoS not supported" in the 5GSM capability IE of the PDU SESSION MODIFICATION REQUEST message. The UE shall not indicate support for reflective QoS for this PDU Session for the remaining lifetime of the PDU Session.

For a PDN connection established when in S1 mode, after an inter-system change from S1 mode to N1 mode, if the UE is a UE operating in single-registration mode in a network supporting N26 interface, the PDU session is of "IPv6" or "IPv4v6" PDU session type, the PDU session is not associated with the control plane only indication:

1. the UE is performing the PDU session modification procedure to indicate the support of Multi-homed IPv6 PDU session and the UE has not previously successfully performed the UE-requested PDU session modification to provide this indication, the UE shall set the MH6-PDU bit to "Multi-homed IPv6 PDU session supported" in the 5GSM capability IE of the PDU SESSION MODIFICATION REQUEST message; or
2. the UE is performing the PDU session modification procedure to indicate that Multi-homed IPv6 PDU session is not supported and the UE has not previously successfully performed the UE-requested PDU session modification to provide this indication, the UE shall set the MH6-PDU bit to "Multi-homed IPv6 PDU session not supported" in the 5GSM capability IE of the PDU SESSION MODIFICATION REQUEST message.

For a PDN connection established when in S1 mode, after an inter-system change from S1 mode to N1 mode, if the UE is a UE operating in single-registration mode in a network supporting N26 interface, the PDU session is of "IPv4", "IPv6", "IPv4v6", or "Ethernet" PDU session type, the PDU session is not associated with the control plane only indication, the UE supports more than 16 packet filters for this PDU session, and the UE has not previously successfully performed the UE-requested PDU session modification to provide this indication, the UE shall indicate the maximum number of packet filters supported for the PDU session in the Maximum number of supported packet filters IE of the PDU SESSION MODIFICATION REQUEST message. For a PDN connection established when in S1 mode, after an inter-system change from S1 mode to N1 mode, if the UE is a UE operating in single-registration mode in a network supporting N26 interface, the PDU session is not associated with the control plane only indication, and the UE has not previously successfully performed the UE-requested PDU session modification to include the Integrity protection maximum data rate IE in the PDU SESSION MODIFICATION REQUEST message, the UE shall include the Integrity protection maximum data rate IE in the PDU SESSION MODIFICATION REQUEST message. If the UE is performing the PDU session modification procedure

1. to request the deletion of a non-default QoS rule due to errors in QoS operations or packet filters;
2. to request the deletion of a QoS flow description due to errors in QoS operations; or
3. to request the deletion of a mapped EPS bearer context due to errors in mapped EPS bearer operation, TFT operation or packet filters,

the UE shall include the 5GSM cause IE in the PDU SESSION MODIFICATION REQUEST message as described in subclauses 6.3.2.3, 6.3.2.4 and 6.4.1.3. When the UE-requested PDU session modification procedure is used to indicate a change of 3GPP PS data off UE status for a PDU session, the UE shall include the Extended protocol configuration options IE in the PDU SESSION MODIFICATION REQUEST message and setting the 3GPP PS data off UE status. For a PDN connection established when in S1 mode, after an inter-system change from S1 mode to N1 mode, if the UE is a UE operating in single-registration mode in a network supporting N26 interface, the PDU session is not associated with the control plane only indication, the UE requests the PDU session to be an always-on PDU session in the 5GS and the UE has not previously successfully performed the UE-requested PDU session modification to request this, the UE shall include the Always-on PDU session requested IE and set the value of the IE to "Always-on PDU session requested" in the PDU SESSION MODIFICATION REQUEST message. If the UE supports transfer of port management information containers, the UE shall set the TPMIC bit to "Transfer of port management information containers supported" in the 5GSM capability IE of the PDU SESSION MODIFICATION REQUEST message. If a port management information container needs to be delivered (see TS 23.501 and TS 23.502), the UE shall include a Port management information container IE in the PDU SESSION MODIFICATION REQUEST message. To request re-negotiation of IP header compression configuration, the UE shall include the IP header compression configuration IE in the PDU SESSION MODIFICATION REQUEST message if the network indicated "Control plane CIoT 5GS optimization supported" and "IP header compression for control plane CIoT 5GS optimization supported" in the 5GS network support feature support IE. To request re-negotiation of Ethernet header compression configuration, the UE shall include the Ethernet header compression configuration IE in the PDU SESSION MODIFICATION REQUEST message if the network indicated "Control plane CIoT 5GS optimization supported" and "Ethernet header compression for control plane CIoT 5GS optimization supported" in the 5GS network support feature support IE. After an inter-system change from S1 mode to N1 mode, if:

1. the UE is operating in single-registration mode in the network supporting N26 interface;
2. the PDU session type value of the PDU session type IE is set to "IPv4", "IPv6" or "IPv4v6";
3. the UE indicates "Control plane CIoT 5GS optimization supported" and "IP header compression for control plane CIoT 5GS optimization supported" in the 5GMM capability IE of the REGISTRATION REQUEST message; and
4. the network indicates "Control plane CIoT 5GS optimization supported" and "IP header compression for control plane CIoT 5GS optimization supported" in the 5GS network support feature IE of the REGISTRATION ACCEPT message;

the UE shall initiate the PDU session modification procedure to negotiate the IP header compression configuration and include the IP header compression configuration IE in the PDU SESSION MODIFICATION REQUEST message. The UE shall include the Service-level-AA container IE in the PDU SESSION MODIFICATION REQUEST message, when requesting to modify an established PDU session for C2 communication. In the Service-level-AA container IE, the UE shall include:

1. the service-level device ID with the value set to the CAA-level UAV ID of the UE; and
2. if available, the service-level-AA payload with the value set to the C2 authorization payload and the service-level-AA payload type with the value set to "C2 authorization payload".

The UE may include the Non-3GPP delay budget IE in the PDU SESSION MODIFICATION REQUEST message, when requesting to modify an established PDU session for PIN-DN communication or PIN indirect commmunication. After an inter-system change from S1 mode to N1 mode, if:

1. the UE is operating in single-registration mode in a network that supports N26 interface;
2. the PDU session type value of the PDU session type IE is set to "Ethernet";
3. the UE indicates "Control plane CIoT 5GS optimization supported" and "Ethernet header compression for control plane CIoT 5GS optimization supported" in the 5GMM capability IE of the REGISTRATION REQUEST message; and
4. the network indicates "Control plane CIoT 5GS optimization supported" and "Ethernet header compression for control plane CIoT 5GS optimization supported" in the 5GS network support feature IE of the REGISTRATION ACCEPT message;

the UE shall initiate the PDU session modification procedure to negotiate the Ethernet header compression configuration and include the Ethernet header compression configuration IE in the PDU SESSION MODIFICATION REQUEST message. For a PDN connection established when in S1 mode, after an inter-system change from S1 mode to N1 mode, and if the UE is a UE operating in single-registration mode in a network supporting N26 interface, and the UE supports receiving DNS server addresses in protocol configuration options and the UE has not previously successfully performed the UE-requested PDU session modification to indicate this support, the UE shall include the Extended protocol configuration options IE in the PDU SESSION MODIFICATION REQUEST message and:

1. if the PDU session is of "IPv4" or "IPv4v6" PDU session type, the UE shall include the DNS server IPv4 address request; and
2. if the PDU session is of "IPv6" or "IPv4v6" PDU session type, the UE shall include the DNS server IPv6 address request.

For a PDN connection established when in S1 mode, after an inter-system change from S1 mode to N1 mode, and if the UE is a UE operating in single-registration mode in a network supporting N26 interface, and the UE supports the EAS rediscovery and the UE has not previously successfully performed the UE-requested PDU session modification to indicate this support, the UE shall include the Extended protocol configuration options IE in the PDU SESSION MODIFICATION REQUEST message and shall include the EAS rediscovery support indication in the Extended protocol configuration options IE. For a PDN connection established when in S1 mode, after an inter-system change from S1 mode to N1 mode, and if the UE is a UE operating in single-registration mode in a network supporting N26 interface, and the UE supports the EDC and the UE has not previously successfully performed the UE-requested PDU session modification to indicate this support, then the UE shall include the Extended protocol configuration options IE in the PDU SESSION MODIFICATION REQUEST message and shall include the EDC support indicator in the Extended protocol configuration options IE. If the UE supports reporting of URSP rule enforcement and is indicated to send URSP rule enforcement report to network based on the matching URSP rule which contains the URSP rule enforcement report indication set to "URSP rule enforcement report is required", the URSP rule enforcement report is associated to:

1. an established PDU session; or
2. a PDN connection, after an inter-system change from S1 mode to N1 mode, and if the UE is a UE operating in single-registration mode in a network supporting N26 interface, the matching URSP rule is newly enforced while the UE was in S1 mode,

then the UE shall include the URSP rule enforcement reports IE in the PDU SESSION MODIFICATION REQUEST message. The UE shall transport:

1. the PDU SESSION MODIFICATION REQUEST message;
2. the PDU session ID; and
3. if the UE-requested PDU session modification:
   1. is not initiated to indicate a change of 3GPP PS data off UE status associated to a PDU session, then the request type set to "modification request"; and
   2. is initiated to indicate a change of 3GPP PS data off UE status associated to a PDU session, then without transporting the request type;

using the NAS transport procedure as specified in subclause 5.4.5, and the UE shall start timer T3581 (see example in Figure 6.4.2.2.1). For a PDN connection established when in S1 mode and not associated with the control plane only indication, after inter-system change from S1 mode to N1 mode, if the UE is registered in a network supporting the ATSSS,

1. the UE may request to modify a PDU session to an MA PDU session; or
2. the UE may allow the network to upgrade the PDU session to an MA PDU session. In order for the UE to allow the network to upgrade the PDU session to an MA PDU session, the UE shall set "MA PDU session network upgrade is allowed" in the MA PDU session information IE and set the request type to "modification request" in the UL NAS TRANSPORT message.

In case the UE executes case a) or b):

1. if the UE supports ATSSS Low-Layer functionality with any steering mode (i.e., any steering mode allowed for ATSSS Low-Layer functionality) as specified in subclause 5.32.6 of TS 23.501, the UE shall set the ATSSS-ST bits to "ATSSS Low-Layer functionality with any steering mode allowed for ATSSS-LL supported" in the 5GSM capability IE of the PDU SESSION MODIFICATION REQUEST message;
2. if the UE supports MPTCP functionality with any steering mode and ATSSS-LL functionality with only active-standby steering mode as specified in subclause 5.32.6 of TS 23.501, the UE shall set the ATSSS-ST bits to "MPTCP functionality with any steering mode and ATSSS-LL functionality with only active-standby steering mode supported" in the 5GSM capability IE of the PDU SESSION MODIFICATION REQUEST message;
3. if the UE supports MPTCP functionality with any steering mode and ATSSS-LL functionality with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality)as specified in subclause 5.32.6 of TS 23.501, the UE shall set the ATSSS-ST bits to "MPTCP functionality with any steering mode and ATSSS-LL functionality with any steering mode allowed for ATSSS-LL supported" in the 5GSM capability IE of the PDU SESSION MODIFICATION REQUEST message;
4. if a performance measurement function in the UE can perform access performance measurements using the QoS flow of the non-default QoS rule as specified in subclause 5.32.5 of TS 23.501, the UE shall set the APMQF bit to "Access performance measurements per QoS flow supported" in the 5GSM capability IE of the PDU SESSION MODIFICATION REQUEST message;
5. if the UE supports MPQUIC functionality with any steering mode and ATSSS-LL functionality with only active-standby steering mode as specified in subclause 5.32.6 of TS 23.501, the UE shall set the ATSSS-ST bits to "MPQUIC functionality with any steering mode and ATSSS-LL functionality with only active-standby steering mode supported" in the 5GSM capability IE of the PDU SESSION MODIFICATION REQUEST message;
6. if the UE supports MPQUIC functionality with any steering mode and ATSSS-LL functionality with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality) as specified in subclause 5.32.6 of TS 23.501, the UE shall set the ATSSS-ST bits to "MPQUIC functionality with any steering mode and ATSSS-LL functionality with any steering mode allowed for ATSSS-LL supported" in the 5GSM capability IE of the PDU SESSION MODIFICATION REQUEST message;
7. if the UE supports MPTCP functionality with any steering mode, MPQUIC functionality with any steering mode and ATSSS-LL functionality with only active-standby steering mode as specified in subclause 5.32.6 of TS 23.501, the UE shall set the ATSSS-ST bits to "MPTCP functionality with any steering mode, MPQUIC functionality with any steering mode and ATSSS-LL functionality with only active-standby steering mode supported" in the 5GSM capability IE of the PDU SESSION MODIFICATION REQUEST message; and
8. if the UE supports MPTCP functionality with any steering mode, MPQUIC functionality with any steering mode and ATSSS-LL functionality with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality) as specified in subclause 5.32.6 of TS 23.501, the UE shall set the ATSSS-ST bits to "MPTCP functionality with any steering mode, MPQUIC functionality with any steering mode and ATSSS-LL functionality with any steering mode allowed for ATSSS-LL supported" in the 5GSM capability IE of the PDU SESSION MODIFICATION REQUEST message.

Upon receipt of a PDU SESSION MODIFICATION REQUEST message for MA PDU session modification, the SMF shall check if the 5GSM capability IE in the PDU SESSION MODIFICATION REQUEST message, includes:

1. the ATSSS-ST bits set to "MPTCP functionality with any steering mode and ATSSS-LL functionality with only active-standby steering mode supported" and:
   1. if the DNN configuration allows for the MPTCP functionality with any steering mode and ATSSS-LL functionality with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality) but does not allow RTT measurement without using PMF protocol, the SMF shall ensure that the modified PDU session has the capability of MPTCP with any steering mode and ATSSS-LL with only active-standby steering mode, load balancing steering mode or priority based steering mode in the downlink and MPTCP with any steering mode and ATSSS-LL with only active-standby steering mode in the uplink;
   2. if the DNN configuration allows for the MPTCP functionality with any steering mode and ATSSS-LL functionality with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality) and allows RTT measurement without using PMF protocol, the SMF shall ensure that the modified PDU session has the capability of MPTCP with any steering mode and ATSSS-LL with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality) in the downlink and MPTCP with any steering mode and ATSSS-LL with only active-standby steering mode in the uplink; or
   3. if the DNN configuration allows for the MPTCP functionality with any steering mode and ATSSS-LL functionality with only active-standby steering mode, the SMF shall ensure that the modified PDU session has the capability of MPTCP with any steering mode and ATSSS-LL with only active-standby steering mode in the downlink and the uplink;
2. the ATSSS-ST bits set to "MPQUIC functionality with any steering mode and ATSSS-LL functionality with only active-standby steering mode supported" and:
   1. if the DNN configuration allows for the MPQUIC functionality with any steering mode and ATSSS-LL functionality with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality) but does not allow RTT measurement without using PMF protocol, the SMF shall ensure that the modified PDU session has the capability of MPQUIC with any steering mode and ATSSS-LL with only active-standby steering mode, load balancing steering mode or priority based steering mode in the downlink and MPQUIC with any steering mode and ATSSS-LL with only active-standby steering mode in the uplink;
   2. if the DNN configuration allows for the MPQUIC functionality with any steering mode and ATSSS-LL functionality with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality) and allows RTT measurement without using PMF protocol, the SMF shall ensure that the modified PDU session has the capability of MPQUIC with any steering mode and ATSSS-LL with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality) in the downlink and MPQUIC with any steering mode and ATSSS-LL with only active-standby steering mode in the uplink; or
   3. if the DNN configuration allows for the MPQUIC functionality with any steering mode and ATSSS-LL functionality with only active-standby steering mode, the SMF shall ensure that the modified PDU session has the capability of MPQUIC with any steering mode and ATSSS-LL with only active-standby steering mode in the downlink and the uplink;
3. the ATSSS-ST bits set to "MPQUIC functionality with any steering mode and ATSSS-LL functionality with any steering mode allowed for ATSSS-LL supported" and if the DNN configuration allows for the MPQUIC functionality with any steering mode and ATSSS-LL functionality with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality), the SMF shall ensure that the modified PDU session has the capability of MPQUIC with any steering mode and ATSSS-LL with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality) in the downlink and the uplink;
4. the ATSSS-ST bits set to "ATSSS Low-Layer functionality with any steering mode allowed for ATSSS-LL supported" and if the DNN configuration allows for the ATSSS-LL functionality with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality), the SMF shall ensure that the modified PDU session has the capability of ATSSS-LL with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality) in the downlink and the uplink;
5. the ATSSS-ST bits set to "MPTCP functionality with any steering mode and ATSSS-LL functionality with any steering mode allowed for ATSSS-LL supported" and if the DNN configuration allows for the MPTCP functionality with any steering mode and ATSSS-LL functionality with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality), the SMF shall ensure that the modified PDU session has the capability of MPTCP with any steering mode and ATSSS-LL with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality) in the downlink and the uplink;
6. the ATSSS-ST bits set to "MPTCP functionality with any steering mode, MPQUIC functionality with any steering mode and ATSSS-LL functionality with any steering mode allowed for ATSSS-LL supported" and if the DNN configuration allows for the MPTCP functionality with any steering mode, the MPQUIC functionality with any steering mode and ATSSS-LL functionality with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality), the SMF shall ensure that the modified PDU session has the capability of MPTCP with any steering mode, the MPQUIC with any steering mode and ATSSS-LL with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality) in the downlink and the uplink; or
7. the ATSSS-ST bits set to "MPTCP functionality with any steering mode, MPQUIC functionality with any steering mode and ATSSS-LL functionality with only active-standby steering mode supported" and
   1. if the DNN configuration allows for the MPTCP functionality with any steering mode, the MPQUIC functionality with any steering mode and ATSSS-LL functionality with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality) but does not allow RTT measurement without using PMF protocol, the SMF shall ensure that the modified PDU session has the capability of MPTCP with any steering mode, MPQUIC with any steering mode and ATSSS-LL with only active-standby steering mode, load balancing steering mode or priority based steering mode in the downlink and MPTCP with any steering mode, MPQUIC with steering mode and ATSSS-LL with only active-standby steering mode in the uplink;
   2. if the DNN configuration allows for the MPTCP functionality with any steering mode, the MPQUIC functionality with any steering mode and ATSSS-LL functionality with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality) and allows RTT measurement without using PMF protocol, the SMF shall ensure that the modified PDU session has the capability of MPTCP with any steering mode, MPQUIC with any steering mode and ATSSS-LL with any steering mode (i.e., any steering mode allowed for ATSSS-LL functionality) in the downlink and MPTCP with any steering mode, MPQUIC with steering mode and ATSSS-LL with only active-standby steering mode in the uplink; or
   3. if the DNN configuration allows for the MPTCP functionality with any steering mode, the MPQUIC functionality with any steering mode and ATSSS-LL functionality with only active-standby steering mode, the SMF shall ensure that the modified PDU session has the capability of MPTCP with any steering mode, MPQUIC with any steering mode and ATSSS-LL with only active-standby steering mode in the downlink and the uplink.

Upon receipt of a PDU SESSION MODIFICATION REQUEST message, if the SMF accepts the request to modify the PDU session, the SMF shall perform the network-requested PDU session modification procedure as specified in subclause 6.3.2. If the PDU SESSION MODIFICATION REQUEST message contains a Port management information container IE, the SMF shall handle the contents of the Port management information container IE as specified in TS 23.501 and TS 23.502.

The following abnormal cases can be identified:

The following abnormal cases can be identified:

1. If the PDU session is an emergency PDU session and the 5GSM cause IE is not included in the PDU SESSION MODIFICATION REQUEST message which is not triggered according to subclause 6.4.2.1, item e), or is set to a 5GSM cause other than the 5GSM causes #41, #42, #44, #45, #83, #84, and #85, the SMF shall reject the PDU SESSION MODIFICATION REQUEST message with 5GSM cause #31 "request rejected, unspecified".
2. PDU session inactive for the received PDU session identity.
   If the PDU session ID in the PDU SESSION MODIFICATION REQUEST message belongs to any PDU session in state PDU SESSION INACTIVE in the SMF, the SMF shall set the 5GSM cause IE to #43 "Invalid PDU session identity" in the PDU SESSION MODIFICATION REJECT message.
3. Collision of network-requested PDU session modification procedure and UE-requested PDU session modification procedure.
   The handling of the same abnormal case as described in subclause 6.3.2.5 applies.
4. AMF provides a "message was exempted from the DNN based congestion activated in the AMF" but the UE-requested PDU session modification procedure is not exempt from DNN based congestion control.
   If the SMF receives an exemptionInd attribute indicating "message was exempted from the DNN based congestion activated in the AMF" as specified in TS 29.502, and the Extended protocol configuration options IE of the PDU SESSION MODIFICATION REQUEST message does not indicate 3GPP PS data off UE status, then the SMF shall set the 5GSM cause #26 "insufficient resources" in the PDU SESSION MODIFICATION REJECT message.
5. AMF provides a "message was exempted from the S-NSSAI and DNN based congestion activated in the AMF" but the UE-requested PDU session modification procedure is not exempt from S-NSSAI only based congestion control.
   If the SMF receives an exemptionInd attribute indicating "message was exempted from the S-NSSAI and DNN based congestion activated in the AMF" as specified in TS 29.502, and the Extended protocol configuration options IE of the PDU SESSION MODIFICATION REQUEST message does not indicate 3GPP PS data off UE status, then the SMF shall set the 5GSM cause #67 "insufficient resources for specific slice and DNN" in the PDU SESSION MODIFICATION REJECT message.
6. AMF provides a "message was exempted from the S-NSSAI only based congestion activated in the AMF" but the UE-requested PDU session modification procedure is not exempt from S-NSSAI only based congestion control.
   If the SMF receives an exemptionInd attribute indicating "message was exempted from the S-NSSAI only based congestion activated in the AMF" as specified in TS 29.502, and the Extended protocol configuration options IE of the PDU SESSION MODIFICATION REQUEST message does not indicate 3GPP PS data off UE status, then the SMF shall set the 5GSM cause #69 "insufficient resources for specific slice" in the PDU SESSION MODIFICATION REJECT message.
7. 5G access network cannot forward the message.
   If the SMF determines based on content of the n2SmInfo attribute specified in TS 29.502 that the DL NAS TRANSPORT message carrying the PDU SESSION MODIFICATION COMMAND message was not forwarded to the UE by the 5G access network due to a cause other than handover procedure in progress, then the SMF shall reject the UE-requested PDU session modification procedure with an appropriate 5GSM cause value in the PDU SESSION MODIFICATION REJECT message.

The purpose of the UE-requested PDU session release procedure is to enable by the UE to request a release of a PDU session. The UE is allowed to initiate the PDU session release procedure even if the timer T3396 is running. The UE is allowed to initiate the PDU session release procedure even if the timer T3584 is running. The UE is allowed to initiate the PDU session release procedure even if the timer T3585 is running. The UE is allowed to initiate the PDU session release procedure even if the UE is outside the LADN service area.

In order to initiate the UE-requested PDU session release procedure, the UE shall create a PDU SESSION RELEASE REQUEST message. The UE may set the 5GSM cause IE of the PDU SESSION RELEASE REQUEST message to indicate the reason for releasing the PDU session. The 5GSM cause IE typically indicates one of the following 5GSM cause values: The UE shall allocate a PTI value currently not used and shall set the PTI IE of the PDU SESSION RELEASE REQUEST message to the allocated PTI value. The UE shall transport the PDU SESSION RELEASE REQUEST message and the PDU session ID, using the NAS transport procedure as specified in subclause 5.4.5, and the UE shall start timer T3582 (see example in Figure 6.4.3.2.1). If the UE is releasing the PDU session due to:

1. errors in QoS operations or packet filters; or
2. the number of the authorized QoS rules, the number of the packet filters, or the number of the authorized QoS flow descriptions associated with the PDU session have reached the maximum number supported by the UE,

the UE shall include the 5GSM cause IE in the PDU SESSION RELEASE REQUEST message as described in subclauses 6.3.2.4 and 6.4.1.3.

Upon receipt of a PDU SESSION RELEASE REQUEST message and a PDU session ID, if the SMF accepts the request to release the PDU session, and shall perform the network-requested PDU session release procedure as specified in subclause 6.3.3.

Upon receipt of a PDU SESSION RELEASE REQUEST message, if the SMF does not accept the request to release the PDU session, the SMF shall create a PDU SESSION RELEASE REJECT message. The SMF shall set the 5GSM cause IE of the PDU SESSION RELEASE REJECT message to indicate the reason for rejecting the PDU session release. The 5GSM cause IE typically indicates one of the following SM cause values: The SMF shall send the PDU SESSION RELEASE REJECT message. Upon receipt of a PDU SESSION RELEASE REJECT message and a PDU session ID, using the NAS transport procedure as specified in subclause 5.4.5, the UE shall stop timer T3582, release the allocated PTI value and locally release the PDU session. If there is one or more multicast MBS sessions associated with the PDU session, the UE shall locally leave the associated multicast MBS sessions.

The following abnormal cases can be identified:

The following abnormal cases can be identified:

1. PDU session inactive for the received PDU session identity.
   If the PDU session ID in the PDU SESSION RELEASE REQUEST message belongs to any PDU session in state PDU SESSION INACTIVE in the SMF, the SMF shall send the PDU SESSION RELEASE REJECT message to the UE with the 5GSM cause #43 "Invalid PDU session identity".